Isaac Levy | bc7dfb5 | 2011-06-06 15:34:01 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2011 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package com.android.server; |
| 18 | |
| 19 | import android.content.ContentResolver; |
| 20 | import android.content.Context; |
| 21 | import android.net.ConnectivityManager; |
| 22 | import android.net.LinkProperties; |
| 23 | import android.os.SystemClock; |
| 24 | import android.util.Slog; |
| 25 | |
| 26 | import java.net.DatagramPacket; |
| 27 | import java.net.DatagramSocket; |
| 28 | import java.net.InetAddress; |
| 29 | import java.net.SocketTimeoutException; |
| 30 | import java.util.Collection; |
| 31 | import java.util.Random; |
| 32 | |
| 33 | /** |
| 34 | * Performs a simple DNS "ping" by sending a "server status" query packet to the |
| 35 | * DNS server. As long as the server replies, we consider it a success. |
| 36 | * <p> |
| 37 | * We do not use a simple hostname lookup because that could be cached and the |
| 38 | * API may not differentiate between a time out and a failure lookup (which we |
| 39 | * really care about). |
| 40 | * <p> |
Isaac Levy | b1ef292 | 2011-06-27 10:02:50 -0700 | [diff] [blame^] | 41 | * TODO : More general API. Socket does not bind to specified connection type |
Isaac Levy | bc7dfb5 | 2011-06-06 15:34:01 -0700 | [diff] [blame] | 42 | * TODO : Choice of DNS query location - current looks up www.android.com |
| 43 | * |
| 44 | * @hide |
| 45 | */ |
| 46 | public final class DnsPinger { |
| 47 | private static final boolean V = true; |
| 48 | |
| 49 | /** Number of bytes for the query */ |
| 50 | private static final int DNS_QUERY_BASE_SIZE = 33; |
| 51 | |
| 52 | /** The DNS port */ |
| 53 | private static final int DNS_PORT = 53; |
| 54 | |
| 55 | /** Used to generate IDs */ |
| 56 | private static Random sRandom = new Random(); |
| 57 | |
| 58 | private ConnectivityManager mConnectivityManager = null; |
| 59 | private ContentResolver mContentResolver; |
| 60 | private Context mContext; |
Isaac Levy | b1ef292 | 2011-06-27 10:02:50 -0700 | [diff] [blame^] | 61 | private int mConnectionType; |
Isaac Levy | bc7dfb5 | 2011-06-06 15:34:01 -0700 | [diff] [blame] | 62 | |
| 63 | private String TAG; |
| 64 | |
Isaac Levy | b1ef292 | 2011-06-27 10:02:50 -0700 | [diff] [blame^] | 65 | |
| 66 | /** |
| 67 | * @param connectionType The connection type from @link {@link ConnectivityManager} |
| 68 | */ |
| 69 | public DnsPinger(String TAG, Context context, int connectionType) { |
Isaac Levy | bc7dfb5 | 2011-06-06 15:34:01 -0700 | [diff] [blame] | 70 | mContext = context; |
| 71 | mContentResolver = context.getContentResolver(); |
Isaac Levy | b1ef292 | 2011-06-27 10:02:50 -0700 | [diff] [blame^] | 72 | mConnectionType = connectionType; |
Isaac Levy | bc7dfb5 | 2011-06-06 15:34:01 -0700 | [diff] [blame] | 73 | this.TAG = TAG; |
| 74 | } |
| 75 | |
| 76 | /** |
Isaac Levy | b1ef292 | 2011-06-27 10:02:50 -0700 | [diff] [blame^] | 77 | * @return The first DNS in the link properties of the specified connection type |
Isaac Levy | bc7dfb5 | 2011-06-06 15:34:01 -0700 | [diff] [blame] | 78 | */ |
| 79 | public InetAddress getDns() { |
Isaac Levy | b1ef292 | 2011-06-27 10:02:50 -0700 | [diff] [blame^] | 80 | LinkProperties linkProperties = getCurLinkProperties(); |
Isaac Levy | bc7dfb5 | 2011-06-06 15:34:01 -0700 | [diff] [blame] | 81 | if (linkProperties == null) |
| 82 | return null; |
| 83 | |
| 84 | Collection<InetAddress> dnses = linkProperties.getDnses(); |
| 85 | if (dnses == null || dnses.size() == 0) |
| 86 | return null; |
| 87 | |
| 88 | return dnses.iterator().next(); |
| 89 | } |
| 90 | |
Isaac Levy | b1ef292 | 2011-06-27 10:02:50 -0700 | [diff] [blame^] | 91 | private LinkProperties getCurLinkProperties() { |
| 92 | if (mConnectivityManager == null) { |
| 93 | mConnectivityManager = (ConnectivityManager) mContext.getSystemService( |
| 94 | Context.CONNECTIVITY_SERVICE); |
| 95 | } |
| 96 | return mConnectivityManager.getLinkProperties(mConnectionType); |
| 97 | } |
| 98 | |
Isaac Levy | bc7dfb5 | 2011-06-06 15:34:01 -0700 | [diff] [blame] | 99 | /** |
| 100 | * @return time to response. Negative value on error. |
| 101 | */ |
| 102 | public long pingDns(InetAddress dnsAddress, int timeout) { |
| 103 | DatagramSocket socket = null; |
| 104 | try { |
| 105 | socket = new DatagramSocket(); |
| 106 | |
| 107 | // Set some socket properties |
| 108 | socket.setSoTimeout(timeout); |
| 109 | |
| 110 | byte[] buf = new byte[DNS_QUERY_BASE_SIZE]; |
| 111 | fillQuery(buf); |
| 112 | |
| 113 | // Send the DNS query |
| 114 | |
| 115 | DatagramPacket packet = new DatagramPacket(buf, |
| 116 | buf.length, dnsAddress, DNS_PORT); |
| 117 | long start = SystemClock.elapsedRealtime(); |
| 118 | socket.send(packet); |
| 119 | |
| 120 | // Wait for reply (blocks for the above timeout) |
| 121 | DatagramPacket replyPacket = new DatagramPacket(buf, buf.length); |
| 122 | socket.receive(replyPacket); |
| 123 | |
| 124 | // If a timeout occurred, an exception would have been thrown. We |
| 125 | // got a reply! |
| 126 | return SystemClock.elapsedRealtime() - start; |
| 127 | |
| 128 | } catch (SocketTimeoutException e) { |
| 129 | // Squelch this exception. |
| 130 | return -1; |
| 131 | } catch (Exception e) { |
| 132 | if (V) { |
| 133 | Slog.v(TAG, "DnsPinger.pingDns got socket exception: ", e); |
| 134 | } |
| 135 | return -2; |
| 136 | } finally { |
| 137 | if (socket != null) { |
| 138 | socket.close(); |
| 139 | } |
| 140 | } |
| 141 | |
| 142 | } |
| 143 | |
| 144 | private static void fillQuery(byte[] buf) { |
| 145 | |
| 146 | /* |
| 147 | * See RFC2929 (though the bit tables in there are misleading for us. |
| 148 | * For example, the recursion desired bit is the 0th bit for us, but |
| 149 | * looking there it would appear as the 7th bit of the byte |
| 150 | */ |
| 151 | |
| 152 | // Make sure it's all zeroed out |
| 153 | for (int i = 0; i < buf.length; i++) |
| 154 | buf[i] = 0; |
| 155 | |
| 156 | // Form a query for www.android.com |
| 157 | |
| 158 | // [0-1] bytes are an ID, generate random ID for this query |
| 159 | buf[0] = (byte) sRandom.nextInt(256); |
| 160 | buf[1] = (byte) sRandom.nextInt(256); |
| 161 | |
| 162 | // [2-3] bytes are for flags. |
| 163 | buf[2] = 1; // Recursion desired |
| 164 | |
| 165 | // [4-5] bytes are for the query count |
| 166 | buf[5] = 1; // One query |
| 167 | |
| 168 | // [6-7] [8-9] [10-11] are all counts of other fields we don't use |
| 169 | |
| 170 | // [12-15] for www |
| 171 | writeString(buf, 12, "www"); |
| 172 | |
| 173 | // [16-23] for android |
| 174 | writeString(buf, 16, "android"); |
| 175 | |
| 176 | // [24-27] for com |
| 177 | writeString(buf, 24, "com"); |
| 178 | |
| 179 | // [29-30] bytes are for QTYPE, set to 1 |
| 180 | buf[30] = 1; |
| 181 | |
| 182 | // [31-32] bytes are for QCLASS, set to 1 |
| 183 | buf[32] = 1; |
| 184 | } |
| 185 | |
| 186 | private static void writeString(byte[] buf, int startPos, String string) { |
| 187 | int pos = startPos; |
| 188 | |
| 189 | // Write the length first |
| 190 | buf[pos++] = (byte) string.length(); |
| 191 | for (int i = 0; i < string.length(); i++) { |
| 192 | buf[pos++] = (byte) string.charAt(i); |
| 193 | } |
| 194 | } |
| 195 | } |